http://lifeaftertheoilcrash.net/ I think I will let the link speak for itself. But please don't read two paragraphs and make an assumption about it, if you read it all you will find it is very intelligent and makes great conclusions.
The issue is not one of "running out" so much as it is not having enough to keep our economy running. In this regard, the ramifications of Peak Oil for our civilization are similar to the ramifications of dehydration for the human body. The human body is 70 percent water. The body of a 200 pound man thus holds 140 pounds of water. Because water is so crucial to everything the human body does, the man doesn't need to lose all 140 pounds of water weight before collapsing due to dehydration. A loss of as little as 10-15 pounds of water may be enough to kill him.
In a similar sense, an oil-based economy such as ours doesn't have to deplete its entire reserve of oil before it begins to collapse. A shortfall between demand and supply as little as 10-15 percent is enough to wholly shatter an oil-dependent economy and reduce its citizenry to poverty.